Civil Engineering Reference
In-Depth Information
f
s
q
c
friction,
f
(MN/m²)
s
q
(MN/m²)
R =
x 100(%)
c
f
0.4
0.3
0.2
0.10.05
2
4
6
8 10
20
10 9 8 7 6 54321 0
0
Ground level
-5
-10
-15
-20
-25
-30
-35
Cone type:
cylindrical electric (R)
Figure 2.11
Typical plot from a cone penetration test (after Meigh 1987)
sleeve friction, f
s
, are recorded by the penetrometer tip (Figures 2.10a&b).
The cone angle on the penetrometer tip is 60
and the cross sectional area
is 1000 mm
2
. There are different types of equipment available on the market
to conduct this test, but the most common involves a 20 tonne truck, to
push the penetrometer tip into the ground.
A typical plot from a CPT is shown in Figure 2.11. The friction ratio,
R
f
is the ratio of the sleeve friction divided by the cone tip resistance,
i.e. R
f
= f
s
/q
c
. The zone in Figure 2.11 where the f
s
and q
c
values are higher
indicate stiffer ground.
It has been found that by plotting the values of q
c
against R
f
an approx-
imate description of the soil type can be obtained (Figure 2.12). Other
relationships have been developed over the years between q
c
and a number
of other parameters, for example undrained shear strength, and angle of
